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INTRODUCTION: Enzyme replacement therapy (ERT) is the standard treatment for patients with Pompe disease, a hereditary metabolic myopathy. While ERT in the home situation is increasingly common in adults with Pompe disease, experience in children remains limited due to higher dosing requirements and increased risk of infusion-associated reactions (IARs). We analysed the results of the in-hospital and home-based infusion programme applied in the Netherlands to children since 1999 to provide guidance. METHODS: We studied hospital and home-based infusions administered to children with Pompe disease (i.e., classic infantile, atypical infantile, and childhood onset phenotypes) who started ERT between 1999 and 2022 and analysed the characteristics of patients and IARs. The IARs were graded by healthcare providers. RESULTS: A total of 11,898 infusions with recombinant human α -glucosidase (rhGAA) were administered in 52 Pompe patients (27 classic infantile, two atypical infantile and 23 childhood onset phenotypes). Of these, 5278 infusions (44.4%) were given in hospital and 6620 (55.6%) were administered at home. IARs occurred in 458 hospital infusions (8.7%) and 110 home infusions (1.7%). The majority of IARs (87.1%) occurred in patients with the classic infantile phenotype. Most IARs were mild; only 21 severe IARs were reported, two of which occurred at home. All IARs could be managed adequately. CONCLUSION: Recombinant human α-glucosidase can be safely administered at home using our protocol in children with Pompe disease, including those with classic infantile Pompe disease who are more likely to develop IAR, provided that in-hospital treatment has been shown to be safe, and the appropriate infrastructure and clinical support are in place.

UNLABELLED: Late-onset Pompe disease (LOPD) is a progressive myopathy. Enzyme replacement therapy is effective, but long-term outcomes vary. Avalglucosidase alfa, shown to be non-inferior to alglucosidase alfa in a phase 3 trial, became available in France through compassionate use for patients with insufficient response to alglucosidase alfa. METHODS: Data from the French Pompe registry were analyzed for patients who switched to avalglucosidase alfa with at least 1 year of follow-up. Respiratory function (forced vital capacity, FVC) and motor function evaluated with gait performance (Six-Minute Walk Test, 6MWT) were assessed before the switch, and one and 2 years after. Individual changes were compared using paired-sample tests. RESULTS: Forty-seven adult patients were included. A stabilization of motor decline was observed: prior to switching, the 6MWT decreased by -27 m/year, whereas an improvement of +17 m/year was seen during the first year after the switch (p = 0.001), followed by overall stability in the second year (-10 m/year, p = 0.280). Respiratory changes were not statistically significant: a decline of 60 mL/year before the switch versus 10 mL/year after 1 year (p = 0.161), and 20 mL/year during the second year (p = 0.346). Three patients died during follow-up, with causes unrelated to the disease or treatment. DISCUSSION: Gait deterioration halted during the first year after transitioning to avalglucosidase, with sustained stabilization thereafter, while respiratory parameters showed minimal change. For patients experiencing significant walking decline under alglucosidase alfa therapy, switching to avalglucosidase alfa resulted in disease stabilization, beginning with mild improvement in the first year and a return to pre-switch baseline thereafter.

Aim: Late-onset Pompe disease (LOPD) is a rare lysosomal disease primarily impacting muscle strength and respiratory function. LOPD has a substantial burden despite the availability of alglucosidase alfa (alg). Patients often require mobility and respiratory support over time. Cipaglucosidase alfa in combination with miglustat (cipa + mig) is one of two more recently approved treatments for adults with LOPD. Given limited data on the lifetime trajectory to mobility and respiratory support in LOPD, a patient-level simulation model was developed to compare the long-term impact of cipa + mig with alg on these outcomes. Materials & methods: The patient-level simulation predicts lifetime mobility and respiratory disease progression outcomes based on the 6-min walk distance and %predicted forced vital capacity for alg and cipa + mig for the overall LOPD population using available data and assumptions from experienced clinicians. PROPEL/PROPEL open-label extension (NCT03729362) and ATB200-02 (NCT02675465) studies informed outcomes for four years with cipa + mig and one year with alg. French Pompe disease registry data were used thereafter. Results: Based on the available data and clinical assumptions, the model predicts cipa + mig slows the overall progression of LOPD, allowing patients an additional 2.72 years without mobility or respiratory support compared with alg. People receiving alg may be wheelchair dependent and require invasive respiratory support for an additional 2.57 and 1.55 years, respectively. Conclusion: Cipa + mig may delay disease progression compared with alg over the lifetime of a patient with LOPD, which would increase the amount of time spent without mobility and respiratory support dependency.

Pompe disease (PD) is a rare, autosomal recessive neuromuscular disorder caused by mutations in the gene encoding acid alpha-glucosidase (GAA). The resulting deficiency in GAA, a lysosomal enzyme, leads to the pathological accumulation of glycogen, primarily in cardiac and skeletal muscles. PD presents as a clinical continuum spanning two major phenotypes: infantile-onset Pompe disease (IOPD), the most severe form, typically characterized by onset before 12 months of age, rapid hypertrophic cardiomyopathy, and severe hypotonia; and late-onset Pompe disease (LOPD), which manifests between 12 months of age and adulthood, and is characterized by progressive axial and proximal muscle weakness and respiratory insufficiency. Enzyme replacement therapy (ERT), available since 2006, has improved survival, particularly in IOPD, but is limited by variable efficacy and limited penetration of the blood-brain barrier, necessitating new approaches. In this comprehensive review, we focus on advances in the understanding and management of PD. First, we explore recent diagnostic advances and the characterization of multisystem involvement in PD. Next, we critically discuss the advantages and limitations of current ERT approaches, and advances achieved with next-generation ERT (avalglucosidase alfa, cipaglucosidase alfa + miglustat). Finally, we summarize cutting-edge, potentially curative strategies, including substrate reduction therapy and novel experimental therapies (e.g., gene therapy) that seek to circumvent the limitations of ERT, provide durable effects, and potentially penetrate the central nervous system.

Pompe disease (PD) results from lysosomal acid α-glucosidase (GAA) deficiency, causing lysosomal glycogen accumulation in cardiac and skeletal muscles. We previously characterized a murine model carrying the orthologous human infantile-onset PD (IOPD) pathogenic variant, c.1826dupA (p.Y609*), introduced into the mouse Gaa gene. Compared to wild-type (WT; C57BL/6NJ) controls, Gaac.1826dupA mice exhibit reduced GAA activity and develop early-onset hypertrophic cardiomyopathy-evidenced by increased left ventricular wall thickness and left ventricular mass index (LVMI)- as well as impaired grip strength and gait abnormalities. To benchmark the model's disease fidelity and assess its responsiveness to established therapeutic intervention, Gaac.1826dupA mice received a single retro-orbital dose of AAV2/8-LSPhGAA (2 × 109 vg/g body weight) at postnatal day 12-14. Twelve weeks post-treatment, mice exhibited supraphysiological GAA enzymatic activity in the heart (550% of WT) and liver (400% of WT) with a 93% reduction in cardiac glycogen. No sex-dependent differences in therapeutic efficacy were observed. Echocardiography revealed robust reversal of cardiac pathology, with wall thicknesses and LVMI values approaching WT levels. In contrast to this profound cardiac rescue, skeletal muscle improvements were modest; while forelimb grip strength remained unchanged, automated gait analysis showed benefit limited to hind paw base of support. These findings demonstrate that the Gaac.1826dupA model mirrors the critical cardiomyopathy characteristic of IOPD. While systemic AAV treatment yields definitive cardiac correction, the partial skeletal muscle response highlights a clear need for optimization. Consequently, the Gaac.1826dupA mouse serves as a high-fidelity platform for evaluating next-generation genomic correction strategies targeting both cardiac and refractory neuromuscular manifestations of PD.